In order to study the relationship between lithology and its composite structure and deformation and failure depth, based on these comprehensive field test data, restricting function of deformation and failure depth to mining coal seam floor by lithology and its composite structure is discussed. The obvious difference characteristics are obtained on homogeneous floor and soft and hard rock composite structure floor. The study results show as follows: 1) The law of deformation and failure of homogeneous floor is relatively simple; the depth of deformation and failure of mining floor is controlled by the strength of floor, and has a gradual characteristics from strong to weak below floor on the whole;2) The deformation and failure floor of soft and hard rock composite structure is complex. There is an obvious restrictive function to the depth of failure floor and deformation degree by the composite structure, weak intercalation being the main weak surface which has strong constraint effect to the depth of failure floor. Namely, soft rock plays an important the effect of the cushion for overlying hard rock, and can produce stress diffusion effect for underlying hard rock. The results show that the floor of lithology and its composite structure has an important restrictive function on the deformation and failure of mining floor depth, and also has theoretical and practical significance to supporting tunnel and preventing water-inrush from mining floor.

In this paper, to evaluate the goaf backfilling effectiveness with solid wastes, the final compression ratio of backfilling materials was proposed as the technical measurement index, and the associated key affected factors were also analyzed. The results show that the three key affected factors of compression ratio include the roof subsidence before backfilling, the gap between the backfilling body and roof, and the compression amount of filling materials. Hereby, to improve the final compression ratio of backfilling materials obviously, the structures and the parameters of filling equipment were optimized, the filling technology was upgraded, and the supervisory control system of compression ratio was also established. The above achievements have been successfully applied in No.12 mine of Pingdingshan coal group. The application results show that the actual final compression ratio of backfilling materials in the goaf is up to 89.4% and the maximum surface subsidence is merely 15 mm, thus ensuring the safety of surface buildings.

This paper dealt with the deformation and failure characteristics of a mining-affected deep coal seam floor by selecting the fully mechanized coal-mining face of the coal mine in the east of Jining City, Shandong Province, China. We numerically simulated and experimentally tested the variation laws of the strain increment with the mining face advancing and the distribution characteristics of the floorâ€™s plastic zone at different depths. The results showed that (1) the failure depth of the mining-troubled floor was between 18 and 20m and the degree of floor failure would further aggravate with face advancing and floor unloading, and (2) the impact of mining pressure on the coal seam floor showed obvious leading and lagging characteristics, and thus its impact region in the coal seam floor could be divided into the elastic and violent disturbance regions. In addition, we numerically simulated and analyzed the mechanism of deformation and failure of the mining floor and showed that simulated results were consistent with the in situ measured results. This study not only provided important information on the roadway supporting of fully mechanized mining tunnels for the prevention of rock bursts, but also provided an important reference value for coal mines with similar geological conditions. Copyright by ASTM Int'l all rights reserved.

With the gradual increase in mining depth and the lower coal seam group mining in North China coalfield, the problems of water inrush into coal mine from the Ordovician carbonatite aquifer underlying the coal seam group and the goaf water flow pollution to the Ordovician carbonatite aquifer are growing seriously. According to systematic statistics and analysis of a large number of geological exploration data in the central coalfield of Yanzhou Shandong Province, author carried out a comprehensive study of the ancient weathering crust impermeability from the weathering crust thickness, drilling core recovery rate, drilling fluid consumption, weathering fracture development and filling degree, geological tectonic development and other aspects of the Middle Ordovician limestone, and established the indicator system to characterize its impermeability, and applied the powerful data management and spatial analysis functions of GIS and information fusion technology to create a GIS-oriented information fusion impermeability evaluation method-aquifuge index method, and put forward technology roadmap and specific work procedures of the aquifuge index method, and has applied the method to a real project.

In order to effectively prevent the pressure bumping accidence occurred when fully-mechanized coalface passed through fault, the SOS microseism monitoring and measuring system was applied to the full time monitoring and measuring on the microseismic activities in the coal and rock mass of the fault area. Based on the variation features of the energy releasing and vibration frequency in the microseismic activities, analyzed active accumulated energy of the fault block affected to the pressure bumping occurred and analyzed the variation law of the microseismic activity influenced by the human mining and excavation in the fault area. The results show that the microseismic activity in the fault tectonic area has a high instability. With the fully-mechanized coalface pass through the fault, the daily seismic release total energy value in the fault area will be steadily increase. The max energy peak will be a tendency to be rapidly increased. Before the strong microseismic activity occurre, there will be a weak seismic activity period and the weak seismic activity will play an energy accumulation role to have a strong seismic to be occurred.